Add comment explaining max_member_access

app/models/group.rb

@@ -551,6 +551,11 @@ class Group < Namespace
   def max_member_access_for_user(user, only_concrete_membership: false)
     return GroupMember::NO_ACCESS unless user
     return GroupMember::OWNER if user.can_admin_all_resources? && !only_concrete_membership
+    # Use the preloaded value that exists instead of performing the db query again(cached or not).
+    # Groups::GroupMembersController#preload_max_access makes use of this by
+    # calling Group#max_member_access. This helps when we have a process
+    # that may query this multiple times from the outside through a policy query
+    # like the GroupPolicy#lookup_access_level! does as a condition for any role
     return user.max_access_for_group[id] if user.max_access_for_group[id]
 
     max_member_access(user)